I felt mine move from the outside 17 weeks...first felt from inside at 11 weeks. Now at 18 weeks, I am feeling distinct kicks on odd occasion, most other movements is just general turning. My husband was able to feel a slight movement himself just the other day too.
I think it depepnds on how much fat you have on your belly too, I'm a size 14 and could feel her myself at around 21 weeks but it was faint, my husband felt her for the first time on Saturday (24 weeks).
To feel the earlier kicks I laid flat on my back and pressed quite firmly with the palm of my hand.
I agree with dogsmom, I had lost weight after having hyperemesis from about 7 weeks and was slim to start off with. Because of that and because I was bed bound a lot, I probably noticed my movement quite early. I also find laying flat on my back and resting my hands (not pressing) on my belly is when I feel it most. My placenta is anterior but I often feel the baby at either side.
First felt mine with my hands around 17 weeks, then more strong and definite at 19w and DH felt it at 20+1. It was definitely harder for him to feel than for me though, as I was also feeling it from the inside and knew what I was looking for.